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DEVELOPMENT OF A MECHATRONIC BLIND STICK

Dan MNDRU, Ion LUNGU, Andrei MOCIRAN, Olimpiu TTARTechnical University of Cluj-Napoca, Faculty of Mechanics

Department: Mechanisms, Fine Mechanics and Mechatronics

400641, Cluj-Napoca, B-dul Muncii 103-105, e-mail: [email protected]

Keywords: visually impaired, guide cane, ultrasonic sensors, tactile stimulation.

Abstract: In this paper, few methods of guiding visually impaired persons are presented. There are analyzedsome commercially available systems which help in locomotion people with disabilities of seeing and giveinformation refereeing to the location of the users. We propose an intelligent stick equipped with anultrasonic sensor that takes information about the environment. This information is processed and isdelivered to the handle stick and thus can be interpreted by the users.

1. INTRODUCTION

The importance of sensorial and communicational functions results from the fact that

the human body is an open biosystem, in a permanent exchange of energy, substancesand information with the environment. The human being receives information from the

environment: 1% by taste, 1,5% by tactile sense, 3,5% by smell, 11% by hear and 83% by

sight, [9].

For an efficient reintegration of the disabled people in the family and society, it is

strongly needful to assist their diminished functions or to replace the totally lost functions.

Thus, a new branch of technology and engineering is developing: Assistive Technology,

meaning any product, instrument, equipment or technical system used by a disabled

person, especially produced or generally available, preventing, compensating, relieving or

neutralizing the impairment, disability or handicap, [3], [8].

Visual impairment refers not just to a total blindness, but to a more common problem

of partial or low vision. It is caused by many different conditions conducting to a variety ofperceptual problems: macular degeneration reduces clarity of central vision, advanced

retinitis pigmentosa produces a tunnel vision, cataracts cloud or blur images, diabetic

retinopathy produces overall dimness, blank or unclear areas, temporary or permanent,

optic nerve atrophy superimposes coloured forms on an image, a.s.o. Because the

problems of visual impairment are much diversified, the solutions for assisting or replacing

the visual sense vary too.

The traditional and oldest mobility aids for persons with visual impairments are the

walking cane (also called white cane or stick) and guide dogs. The most important

drawbacks of these aids are necessary skills and training phase, range of motion and very

little information conveyed.

The aim of this paper is to describe new methods of guiding visually impairedpersons and to present a new low cost system, called mechatronic blind stick which is

easy to use by visually impaired persons.

2. COMPARATIVE STUDY OF SIMILAR PRODUCTS

Several sophisticated guide systems for visually disabled have already beendeveloped. These are based on following methods, [1], [10]:- the equipment on the ground detects a magnet in the users cane and sends a guidemessage by a speaker;

ANNALS of the ORADEA UNIVERSITY.

Fascicle of Management and Technological Engineering, Volume VI (XVI), 2007

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- a sensor in the cane detects magnets on the ground and informs the user by vibration;- a specialized system on the ground detects the signal from a portable transmitter of theuser and sends a guide message by a speaker;- the radio carried by the user catches the broadcasting messages transmitted through anantenna installed in the ground;

- a portable system informs the user of his/her position using GPS signal.

New mobile guide systems that utilize the latest technologies such as data-carriers,mobile communication and portable computers are experimentally tested. Coded data

recorded in data-carriers are transferred to visually disabled users via a reader in the cane;the data are interpreted by a portable computer, which generates guide messages via aportable speaker. For safety of the visually disabled passengers, several systems thatoffer guide messages using speakers installed at fixed places are already in use, but thesemessages are fixed and not adaptive.

According with [2], [4] - [7] and [12] - [18], in Figure 1 there are presented somerepresentative commercially available products designed as mobility aids and guidingsystems for visually impaired persons.

The UltraCane (Fig. 1a) is a vibrating electronic mobility aid and obstacle detector.The cane has the shape of a long white cane with a collapsible shaft and a contoured

a b c

d e f g

h i j

Fig. 1 Examples of representative mobility aids vor visual impaired persons



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handle, and uses ultrasonic echos to detect obstacles ahead of the user, includingobstacles in the user's path and at head level. It converts this information into vibratingbuttons in the handle which tell the user where an object may be and how far away theobstacle lies. The cane can be customized to the user's height.

The 'K' Sonar (Fig. 1b), is an audible electronic mobility aid and obstacle detector.

This small electronic device aids users who are blind or visually impaired with orientationand mobility. By listening to sounds produced by the device, users can determine thedistance and location of objects and some of the object's features. The device attaches tothe golf grip handle of a long cane. Headphones provide audio feedback, which changes inpitch to indicate the distance to the object being scanned.

The Teletact is a hand held laser telemeter (Fig. 1c). The distance to the firstobstacle encountered by the laser beam is measured with about 1% accuracy in the 10cm 10m range. The blind perceives the direction he points thanks to the internalconsciousness of the position of its members (proprioception). To identify an obstacle it isnecessary to scan the environment. So, the rate of distance measurements is 40measurements per second. To communicate to the blind the information of distance, 28different musical notes are used, which correspond to 28 unequal intervals of distances

(intervals are smaller at short distances), the higher the tone, the shorter the distance. Thetelemeter gives a precision of about 1% on the distance measurement. The most importantinformation is not identification of musical notes but the sense and the rate of theirvariations, in other word the transcription of the profile of the obstacles into a melody. Toobtain a silent device the sonorous output is replaced by vibrating devices localised underthe fingers.

The shoes in Figure 1e are equipped with infrared sensors that sense objects up to ameter away and trigger vibrations corresponding to the location and size of obstacles.

The UBG - Ultra Body Guard (Fig. 1f) is a vibrating and voice output electronicmobility aid which detects obstacles at head and upper body level and provides users withtactile or spoken warnings.

The Sonic Pathfinder(Fig. 1g) is an electronic obstacle detector which gives the useradvanced warning of objects which lie within his or her travel path. It is a head-mountedpulse-echo sonar system controlled by a microcomputer, with five ultrasonic transducersmounted on a headband, comprising two transmitters and three receivers, one pointingleft, one right, and one straight ahead. Echoes from objects are received by the threereceiving transducers and this information is processed by the on-board computer. Theoutput is fed to one or other of the two ear pieces.

The LaserCane (Fig. 1h), warns the user of approaching obstacles through audibletones and vibrating stimulators under the index finger. The user has the option of turningthe audible tones off to rely on the vibrating stimulators alone. The cane is used in thesame manner as a long white cane. The cane is operated with one hand, while the otherhand is free for other tasks.

Other systems are given in Figure 1: The Guide Cane (Fig. 1d), Miniguide andPolaron (Fig. 1i) and The VOICE(Fig. 1j). The apparatus composing the above presentedsystems are expensive and often places where they are installed or could be used arerestricted.

3. THE DEVELOPED SYSTEM

The new intelligent blind stick ensures an alternative channel for the sensorial

perception (e.g. tactile sense and hearing, instead of seeing). It is made of a pipe 18 mm

diameter. The pipe is divided in two parts, first has 630 mm length and the second has 720



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+5V

+5V

+5V

+5V

+5V

ResetReset

4MHz

C233p

C333p

C41n

R622k

U1ATtiny2313

145

10

20

1213141516171819

236789

11

RESETXTAL2XTAL1

G

ND

VCC

PB0/AIN0PB1/AIN1

PB2PB3/OC1

PB4PB5/MOSIPB6/MISOPB7/SCK

PD0/RXDPD1/TXDPD2/INTOPD3/INT1PD4/TOPD5/T1PD6/ICP

R51k

C1100n

R3100k

R41k

MK1Buzzer

MK3Emitor

MK2Receiver

R21k

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-

+

Motor DC

Q2BD135

J1STK200

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Fig. 3 The electrical diagram

mm. A plastic box is fixed on the upper part of the stick. Inside of this hull there are the

ultrasonic sensors, the circuitry and the buzzer. The cane weights 450 g. In Figure 2 the

3D model and a picture of the stick are presented.

a b

Fig. 2 The 3D model and a picture of the developed stick

a

bFig. 4a The ultrasonic sensors,

Fig. 4b The piezo buzzer



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The distance from the sensor to an obstacle in front of the stick is detected by theultrasonic sensors which we used: UST 40 type (fig. 4a). These sensors arecharacterized by center frequency 40 kHz, whith a tolerance between 2 kHz andtransmitting sound pressure level 120dB. The electrical diagram is presented in figure 3and the circuit works as follows:

- it is activate the switch on/off ;- it is sent the work frequency (f=40 kHz), three period, realized by timer 0 of

ATtiny2313 microcontroller;- therewith it is activate timer 1;- at first echo impulse received the timer 1 its off and the value (t) recorded its used

to calculate the distance using the relation:

T.vv,vt

d 602

0+== (1)

where we note:v0 the sound velocity at T=0C, v0=331.45 m/sT the temperature.

- the vibration of the handle is produced by a DC motor. We use PWM (Pulse WidthModulation) method to control the miniature DC motor. Width factor is proportionalwith the distance. In figure 5there is presented the diagram for electric impulse.

- its activated the sound alarm. The sound is more intense as the distance issmaller. The piezo buzzer CPB14B09 was used (Fig. 4b);

In figure 6, the layout circuit of this application is given.

CONCLUSIONS

The assistive devices are much diversified due to the diversity of affections, having astrong adaptability to each user. The visually impaired persons, especially the blind

Fig. 5 The impulse diagram

Fig.6 The layout circuit



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people, gather information from the environment through the other valid senses (tactileand hearing sense). One of the improvements which can be brought to classical whitecanes is to equip them with proximity sensors and systems which can be used to transmitinformation shaped like acoustic and tactile signals.

The developed prototype gives good results in detecting obstacles paced at distance

in front of the user. Our efforts are focussed on improving the output signals (vibrationsand sounds), according with the distance.

REFERENCES

[1]. Audette, R., Dunk, C., Zelek, J., A stereo-vision system for the visually impaired, Technical Report 2000-41x-1, School of Eng., University of Guelph, 2000.[2]. Ban, I., Mitsuta, Y., Blind Person Guide Device, U.S. Patent, 1987.[3]. Bronzino, J.D. (editor), Biomedical Engineering Handbook, CRC Press & IEEE Press, Hartford, 1997.[4]. Chi-Sheng, H., Electronic talking stick for the blind, U.S. Patent, 1992.[5]. Elchinger, G. M., Mobility Cane for the Blind Incorporating Ultrasonic Obstacle Sensing Apparatus, U.S.Patent, 1991[6]. Kang, S.J., Ho, Y., Moon, I.H., Development of an Intelligent Guide-Stick for the Blind, Proc. of the 2001IEEE Int. Conf. on Robotics & Automation, Seoul, 2001, pp. 3208 3213.

[7]. Meijer, P., An experimental system for auditory image representations, IEEE Trans. on Biomedical Eng.,vol. 39, 1992, pp. 112 121.[8]. Mandru, D., Ingineria protezarii si reabilitarii, Editura Casa Cartii de Stiinta, Cluj-Napoca, 2001.[9]. Maties, V., Mandru, D., Balan, R., Tatar, O., Rusu, C. Tehnologie si educatie mecatronica, EdituraTodesco, 2001.[10]. Mociran, A., Proiectarea i realizarea unui baston inteligent pentru persoane nevazatoare, Proiect deDiplom, Universitatea Tehnic din Cluj-Napoca, 2006.[11]. Wong, F., Zelek, J., Tactile & Inertial Patterns from a Long White Cane, Proceedings of the InternationalConference BIOROB 2006, Pisa, pp. 372 377.[12]. * * * - K Sonar http://www.abledata.com/abledata.cfm?pageid= 19327&top= 10267&productid=158640 &trail=0[13]. * * * Polaron http://www.abledata.com/abledata.cfm?pageid=19327&top= 15688 &productid = 95519 &trail=0[14]. * * * Sonic Pathfinder http://www.abledata.com/abledata.cfm?pageid=19327&top =10267&productid=

746 26&trail=0[15]. * * * Smart Shoes http://www.usatoday.com/tech/news/techinnovations/2003-03-31- smart-shoes_x.htm[16]. * * * Talking Signs Project. http://www.talkingsigns.com.[17]. * * * Ultra Body Guard http://www.abledata.com/abledata.cfm?pageid=19327&top =15688&productid =75745 & trail=0[18]. * * * Ultracane http://www.abledata.com/abledata.cfm?pageid=19327&top=15688& productid = 113 906&trail=0



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